Question about timing and TDC.

How do you know if you are on the compression stroke or exhaust stroke when you do the top end? I took apart the head and cylinder to replace the intake valves and change rings. I did the scotchbrite thing to clean the cylinder and used the service manual to reassemble, step by step. I have completely reassembled and only need to add radiator fluid to start up. I lined up all the timing marks per manual and tightened the cam sprocket with threadlocker. My guess is if it fires up, all is gravy, but if it doesn't, I reassembled it on the exhaust stroke and the spark plug will fire at the wrong stroke? Is there anyway to know??:smirk:

I don't know for sure on the 450F, but most Hondas I have dealt with fire by a crank pulse so there is no TDC compression stroke fire only. It will fire every revolution so it makes no difference where it's timed as long as the mark match.

If I am wrong I am sure someone smarter than me will sound off and enlighten us both, never fear.

It fires on every stroke.

Thanks for the replies. Everything was lined up and the cam had the lobes to the rear as required when I assembled it. I should be good to go. Thanks.

The cam determines the compression stroke on any engine, when the valves are all closed with the piston up, thats the conpression stroke. on a bike the fire comes from the crank, but it fires every stroke like he said so it doesn't matter.

Just line up the marks with the valves closed and your ok.

Rockers/ buckets should have no pressure on them.

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